1. Field of the Invention
This invention relates to a smoke stop for doors.
2. Description of the Prior Art
It has long been a desire of the construction industry to provide a smoke stop between a closed door and the frame supporting the door. This smoke stop provides numerous advantages. If the smoke stop is effective as a smoke stop, it prevents smoke from passing through the door passage when a fire exists on one side of the door. This feature is extremely important from a health and safety standpoint. An additional advantage of a smoke stop is that it prevents passage of air into the room containing a flame thereby slowing the rate of spread of the flame.
Many attempts have been made to prepare a smoke stop for doors. The first such attempts made use of sealing materials between the frame and the door whereupon closing of the door deformed the seal and at all times closed the gap between the door and the frame. The disadvantage of this type of construction is that at all times the resilient material must contact the closed door, and the opening and closing of the door is thereby impeded. Additionally, wear on the door is caused by the consequent relative frictional movement upon opening and closing the door. If the edge of the door is a decorative surface, i.e., a highly finished painted or varnished section, then the constant contacting with the resilient material upon opening and closing of the door debases this highly decorative surface making it unsightly when the door remains open.
The use of intumescent materials to seal the space between a door and a frame is not novel. Many attempts have been made to utilize intumescent materials, i.e., materials that expand upon application of heat, to overcome the problems associated with the usage of the resilient facings and yet to provide an effective seal between the frame and the door upon contact thereof with a flame. These prior attempts, however, have all fallen short of the intended goal for one or more reasons. The basic failure of the systems has been due to the fact that most of the systems use an exposed intumescent material which upon sufficient heating melts and runs down the door thereby relinquishing its sealing properties. Other systems provide sealing with a combustible material which soons burns away and provides only a temporary solution before again presenting the problem of the material melting and destroying the seal. Still other systems have utilized slots within the frame with the slots containing an exposed intumescent material which upon heating expands and extrudes out of the slots into the space between the door and the frame. This system, however, fails for the same reasons mentioned above, namely, that the material soon melts and the seal becomes inoperative.
Prior issued patents demonstrate that the above-discussed systems have the shortcomings explained with relation thereto. In U.S. Pat. No. 3,774,345, a good example of the resilient contacting-type design is shown. This constant contact and rubbing with the door, however, tends to deface the door and thereby makes this type of system undesirable. Norwegian Pat. No. 66,400 is an early example of an intumescent simply laid upon the door frame itself for expansion upon heating. This system, however, has the consequent shortcomings of the material melting and then not providing an adequate seal between the door and the frame. Likewise, British Pat. No. 896,149 provides a similar system with an intumescent material on the face of the frame, however; one embodiment of this patent does provide an additional support for the intumescent material which prevents expansion in one direction. This system, however, does have the shortcoming of the intumescent material's being able to melt and run out of the sealing area thereby causing a failure of the smoke stop system. British Pat. No. 896,150, provides still another system of placing an intumescent material within a slot in the frame, but this system merely directs the channeling of the intumescent material in a different direction and does not overcome the hereinabove discussed associated problems. Norwegian Pat. No. 104,072, is a system almost identical to the last mentioned British Patent but enclosing the intumescent material in a rapidly decomposable tube which soon burns away thus leading to the same problems discussed in relation to the above-mentioned designs. U.S. Pat. No. 2,910,739, makes use of intumescent materials placed in a slot in the door, but, at best, the improvement therein is one in which wood encloses a portion of the intumescent material causing the obvious problem of the wood's rapidly burning away thereby exposing the intumescent material to flame which readily destroys it and the seal provided thereby. Danish Pat. No. 93,373, provides for an enclosed material, but the intumescent material can only expand through slots in the frame, and after extruding through the slots, the material again creates the problems discussed hereinbefore. U.S. Pat. No. 3,566,541, makes good use of a combination of the prior art systems providing for one exposed strip of intumescent material which has the problems discussed hereinbefore, but which also provides for an enclosed intumescent material sealed within a resilient contacting sealer. This design not only creates permanent contact and frictional wear on the door due to the continuous contact upon closing of the door, but as well, has the problems associated with a decomposable container for the intumescent material which, upon burning, provides the same problems discussed hereinbefore. Likewise, Danish Pat. No. 92,422, provides an intumescent material completely enclosed by a combustible material which upon burning of the combustible material provides the same problems discussed hereinbefore. Finally, U.S. Pat. No. 3,426,491, makes good use of a sandwich-type system for sandwiching the intumescent material between metal and wood, but again, this system fails to prevent ready escape of the intumescent material creating the consequent failure of the seal upon heating. In this invention, intumscent material is enclosed within a slot which has a pivotable lid thereon, and the expansion of the intumescent material presses the pivotable lid against the door, making a sealing contact with the door to prevent smoke from passing into the passage therebetween. In this instance, while the intumescent material may then melt and run out of the slot, it has served its function by forcing the metal plate into a sealing relationship between the frame and the door, and since the metal plate is made of a noncombustible material, the seal remains intact so long as the remaining portions of the door and frame are not destroyed by the heat of the flame itself. It may thus be seen that the new and novel designs of this invention readily overcome the failing features associated with prior systems.